<div class="panel panel-primary">
  <div class="panel-heading">*ngSwitch的用法</div>
  <div class="panel-body">
    <div [ngSwitch]="mapStatus">
      <p *ngSwitchCase="0">下载中</p>
      <p *ngSwitchCase="1">读取中</p>
      <p *ngSwitchDefault>系统繁忙</p>
    </div>
   </div>
</div>
